FIELD OF INDUSTRIAL APPLICABILITY
[0001] The present invention relates to polymorphic forms of Entinostat, processes for their
preparation, compositions comprising them and their medical use.
BACKGROUND OF THE DISCLOSURE
[0002] Histone deacetylase (HDAC) inhibitors are an emerging class of therapeutic agents
that promote differentiation and apoptosis in hematologic and solid malignancies through
chromatin remodeling and gene expression regulation. Entinostat ((pyridin-3-yl)methyl
4-(2-aminophenylcarbamoyl)benzylcarbamate) is a benzamide HDAC inhibitor undergoing
clinical investigation in multiple types of solid tumors, such as breast cancer, and
hematologic cancers. Its chemical preparation is disclosed in example 48 of
EP 847992 A1 and its chemical structure is reported below:

[0003] WO 2009/076206 A1 discloses a process for the preparation of Entinostat. The solid form of the obtained
product is not disclosed. Reproduction of such process affords a mixture of crystal
forms A and B, as disclosed in
WO 2010/022988 A1.
[0004] WO 2010/022988 A1 describes crystalline forms A, B and C of Entinostat and processes for the preparation
of crystalline forms A and B. As disclosed therein, crystal form A is difficult to
obtain in high chemical purity and recrystallization from common solvents, such as
ethanol, methanol and acetonitrile, does not afford a chemically pure substance. It
is further disclosed that crystal form A, not being the thermodynamically most stable
form, is difficult to obtain in polymorphic pure form. Form B should allegedly solve
these problems; however example 1 of
WO 2010/022988 A1 discloses that 15 kg of charcoal for 30 kg of Entinostat are needed in order to achieve
the desired purification. The use of such large amount of charcoal is unusual in the
art and may lead to loss of product absorbed on the charcoal as well as to the production
of unnecessary waste. Indeed the reported yield of such example is only 30-80% of
theory.
[0005] An object of the present invention is thus the provision of a crystalline form of
Entinostat that allows its efficient chemical purification, as well as the provision
of such a purification process. A further object is the provision of a process for
the preparation of crystalline form A with enhanced chemical and polymorphic purity
and free of coloured impurities.
[0006] Entinostat is sparingly soluble in water and its low solubility can make the preparation
of pharmaceutical compositions having adequate dissolution challenging. A further
object of the present invention is thus the provision of a solid form of Entinostat
having improved water solubility and the provision of a pharmaceutical composition
of Entinostat exhibiting improved dissolution in water.
SUMMARY OF THE DISCLOSURE
[0007] The present disclosure provides crystalline forms D and E of Entinostat and a process
for their preparation. It also provides a process for the purification of Entinostat
form A by crystallization and isolation of Entinostat crystal form D and E. Crystal
form D can be obtained in high chemical purity, exhibits improved water solubility
and allows efficient purification of Entinostat with removal of coloured impurities.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
FIG. 1 illustrates the x-ray powder diffraction patterns of crystalline form D.
FIG. 2 illustrates the x-ray powder diffraction patterns of crystalline form E.
FIG. 3 illustrates the DTA/TGA trace of crystalline form D.
FIG. 4 illustrates the DTA/TGA trace of crystalline form E.
FIG. 5 compares the colours of crystal forms A, B and D after compression.
FIG. 6 compares the x-ray powder diffraction patterns of form A and of the material
obtained from reference example 1
DETAILED DESCRIPTION OF THE DISCLOSURE
[0009] The disclosure relates to crystalline forms of Entinostat, which are described and
characterized herein.
Definitions
[0010] As used herein "polymorph" refers to crystalline forms having the same chemical composition
but different spatial arrangements of the molecules, atoms, and/or ions forming the
crystal.
[0011] As used herein "solvate" refers to a crystalline form of a molecule that further
comprises molecules of solvent incorporated into the crystalline lattice structure.
The solvent molecules in the solvate may be present in a regular arrangement and/or
a non-ordered arrangement. The solvate may comprise either a stoichiometric or nonstoichiometric
amount of the solvent molecules. For example, a solvate with a nonstoichiometric amount
of solvent molecules may result from partial loss of solvent from the stoichiometric
solvate. Solvates may occur as dimers or oligomers comprising more than one molecule
or Entinostat within the crystalline lattice structure.
[0012] As used herein, the term "substantially pure" with reference to a particular polymorphic
form means that the polymorphic form includes less than 10%, preferably less than
5%, more preferably less than 3%, most preferably less than 1% by weight of any other
physical forms of the compound.
[0013] The term "essentially the same" with reference to X-ray diffraction peak positions
means that typical peak position and intensity variability are taken into account.
For example, one skilled in the art will appreciate that the peak positions (2θ) will
show some inter-apparatus variability, typically as much as 0.2°. Further, one skilled
in the art will appreciate that relative peak intensities will show inter-apparatus
variability as well as variability due to degree of crystallinity, preferred orientation,
prepared sample surface, and other factors known to those skilled in the art, and
should be taken as qualitative measure only.
Consequently, it is to be understood that the crystal forms of the present invention
are not limited to the crystal forms that provides X-ray diffraction patterns completely
identical to the X-ray diffraction patterns depicted in the accompanying figures disclosed
herein. Any crystal forms that provide X- ray diffraction patterns substantially identical
to those disclosed in the accompanying Figures fall within the scope of the present
invention. The ability to ascertain substantial identities of X-ray diffraction patterns
is within the purview of one of ordinary skill in the art.
[0014] The term "slurry", as used herein, means a saturated solution of the compound, which
may also contain an additional amount of the compound to afford a heterogeneous mixture
of the compound and a solvent at a given temperature.
Crystal form D
[0015] In one embodiment, the present invention provides a crystalline form of Entinostat
having an X-ray diffraction pattern substantially the same as the X-ray powder diffraction
pattern shown in FIG. 1.
[0016] Crystalline form D may be characterized by a X-ray powder diffraction pattern (XRPD)
comprising peaks at 2θ values of 4.8°, 9.8°, 17.2°, 19.7° and 22.9°, measured at a
temperature of about 20°C and using Cu-Kα radiation (wavelength λ= 1.5418 Å).
[0017] Preferably, crystalline form D may be characterized by a x-ray powder diffraction
pattern comprising 2θ values of 4.8°, 9.8°, 12.8°, 14.7°, 17.2°, 18.4°, 19.7°, 21.8°
and 22.9°, measured at a temperature of about 20°C and using Cu-Kα radiation (wavelength
λ= 1.5418 Å).
[0018] The complete listing of peaks and relative intensities are reported in the following
table:
Position 2θ [°] |
Relative intensity [%] |
4.8 |
5.0 |
5.7 |
4.7 |
9.8 |
6.5 |
12.8 |
2.7 |
14.7 |
4.8 |
17.2 |
18.3 |
18.4 |
70.4 |
19.1 |
40 |
19.7 |
45.3 |
20.6 |
13.7 |
21.8 |
57.4 |
22.4 |
8.6 |
22.9 |
100 |
23.8 |
9.7 |
24.8 |
10.5 |
26.2 |
8.4 |
26.8 |
8.7 |
27.5 |
7.2 |
28.7 |
5.4 |
29.5 |
3.8 |
31.0 |
2.0 |
32.1 |
1.9 |
33.8 |
1.2 |
[0019] In one embodiment, the present invention provides a crystalline form D of Entinostat
having a DTA/TGA trace substantially the same as the DTA/TGA trace shown in FIG. 2.
Crystalline form D may be characterized by a DTA/TGA trace showing an exotherm at
115°C and a melting endotherm at 151°C.
[0020] In a preferred embodiment, crystal form D is in substantially pure form. Preferably,
Form D includes less than 10%, more preferably less than 5%, even more preferably
less than 3%, most preferably less than 1% by weight of other crystalline forms, preferably
selected from the group consisting of crystal form A, crystal form B and crystal form
C, wherein form A is characterized by a x-ray powder diffraction pattern (XRPD) comprising
peaks at 2θ values of 18.4°, 18.8°, 19.1°, 20.9°, 22.6°, 26.4°, 26.7° and 27.2°, wherein
form B is characterized by a x-ray powder diffraction pattern (XRPD) comprising peaks
at 2θ values of 9.2°, 18.1 °, 19.4°, 20.0°, 20.4°, 21.1°, 22.1°, 25.8° and 27.4°,
wherein form C is characterized by a x-ray powder diffraction pattern (XRPD) comprising
peaks at 2θ values of 17.7°, 18.4°, 18.8°, 19.2°, 20.0°, 22.0°, 22.3°, 23.2° and 23.4°,
all peaks measured at a temperature of about 20°C and using Cu-Kα radiation (wavelength
λ= 1.5418 Å).
Crystal form E
[0021] In one embodiment, the present invention provides a crystalline form E of Entinostat
having an X-ray diffraction pattern substantially the same as the X-ray powder diffraction
pattern shown in FIG. 3.
[0022] Crystalline form E may be characterized by a X-ray powder diffraction pattern (XRPD)
comprising peaks at 2θ values of 3.8°, 15.3° and 21.6°, measured at a temperature
of about 20°C and using Cu-Kα radiation (wavelength λ= 1.5418 Å).
[0023] Preferably, crystalline form E may be characterized by a x-ray powder diffraction
pattern comprising 2θ values of 3.8°, 15.3°, 18.2°, 21.6°, 23.9° and 24.5°, measured
at a temperature of about 20°C and using Cu-Kα radiation (wavelength λ= 1.5418 Å).
[0024] The complete listing of peaks, their heights and relative intensities are reported
in the following table:
Position 2θ [°] |
Relative intensity [%] |
3.8 |
100.00 |
5.8 |
14.39 |
7.6 |
3.96 |
11.5 |
9.21 |
15.3 |
11.67 |
15.9 |
21.50 |
17.1 |
11.84 |
18.2 |
97.82 |
19.0 |
42.91 |
20.9 |
16.52 |
21.6 |
44.12 |
23.0 |
64.35 |
23.9 |
42.29 |
24.5 |
23.55 |
25.5 |
33.34 |
26.6 |
7.22 |
27.7 |
8.66 |
28.6 |
6.41 |
29.1 |
15.19 |
30.4 |
5.45 |
31.2 |
3.54 |
32.5 |
3.19 |
33.7 |
4.17 |
[0025] In one embodiment, the present invention provides a crystalline form E of Entinostat
having a DTA/TGA trace substantially the same as the DTA/TGA trace shown in FIG. 4.
Crystalline form E may be characterized by a DTA/TGA trace showing an endotherm at
80°C and a melting endotherm at 155°C. Crystal form E is a 1,4-dioxane solvate, preferably
in a 1:1 Entinostat / dioxane ratio.
[0026] In a preferred embodiment, crystal form E is in substantially pure form. Preferably,
Form E includes less than 10%, more preferably less than 5%, even more preferably
less than 3%, most preferably less than 1% by weight of other crystalline forms, preferably
selected from the group consisting of crystal form A, crystal form B and crystal form
C, wherein form A is characterized by a x-ray powder diffraction pattern (XRPD) comprising
peaks at 2θ values of 18.4°, 18.8°, 19.1°, 20.9°, 22.6°, 26.4°, 26.7° and 27.2°, wherein
form B is characterized by a x-ray powder diffraction pattern (XRPD) comprising peaks
at 2θ values of 9.2°, 18.1 °, 19.4°, 20.0°, 20.4°, 21.1°, 22.1°, 25.8° and 27.4°,
wherein form C is characterized by a x-ray powder diffraction pattern (XRPD) comprising
peaks at 2θ values of 17.7°, 18.4°, 18.8°, 19.2°, 20.0°, 22.0°, 22.3°, 23.2° and 23.4°,
all peaks measured at a temperature of about 20°C and using Cu-Kα radiation (wavelength
λ= 1.5418 Å).
Crystal form A in substantially pure form
[0027] In one embodiment, the present invention provides a crystalline form A of Entinostat
in substantially pure form. Form A may be characterized by a x-ray powder diffraction
pattern (XRPD) comprising peaks at 2θ values of 18.4°, 18.8°, 19.1°, 20.9°, 22.6°,
26.4°, 26.7° and 27.2°, measured at a temperature of about 20°C and using Cu-Kα radiation
(wavelength λ= 1.5418 Å).
[0028] Preferably, Form A includes less than 10%, more preferably less than 5%, even more
preferably less than 3%, most preferably less than 1% by weight of other crystalline
forms, preferably selected from the group consisting of crystal form B and crystal
form C, wherein form B is characterized by a x-ray powder diffraction pattern (XRPD)
comprising peaks at 2θ values of 9.2°, 18.1 °, 19.4°, 20.0°, 20.4°, 21.1°, 22.1°,
25.8° and 27.4°, wherein form C is characterized by a x-ray powder diffraction pattern
(XRPD) comprising peaks at 2θ values of 17.7°, 18.4°, 18.8°, 19.2°, 20.0°, 22.0°,
22.3°, 23.2° and 23.4°, all peaks measured at a temperature of about 20°C and using
Cu-Kα radiation (wavelength λ= 1.5418 Å).
Preparation process
[0029] One method to prepare crystalline form E of Entinostat comprises the steps of suspending
and/or dissolving Entinostat in a solvent comprising dioxane, preferably in pure dioxane,
and then isolating crystalline form E. The mixture may be heated to promote dissolution
and the solution volume may then be reduced by evaporation to produce a slurry. The
slurry can be stirred for 12 to 120 hours at room temperature and filtered to provide
crystalline form E.
[0030] One method to prepare crystalline form D of Entinostat comprises the steps of drying
crystalline form E of Entinostat. The drying step is preferably performed under vacuum,
preferably at a temperature below 40°C, more preferably below 35°C, preferably for
more than 1 week, more preferably for more than 2 weeks. Preferably, a fluidized bed
dryer is used. Alternatively, a belt dryer, a rotary dryer or a vacuum tray dryer
with appropriately controlled temperature, cycle time and humidity can be used. Crystalline
form E can thus be used as an intermediate in the preparation of crystalline form
D.
[0031] Crystalline form D of Entinostat can be conveniently converted to crystalline form
A, wherein form A is characterized by a x-ray powder diffraction pattern (XRPD) comprising
peaks at 2θ values of 18.4°, 18.8°, 19.1°, 20.9°, 22.6°, 26.4°, 26.7° and 27.2°, measured
at a temperature of about 20°C and using Cu-Kα radiation (wavelength λ= 1.5418 Å).
One method to prepare crystalline form A of Entinostat comprises the steps of contacting
the crystalline form D of Entinostat of the invention with a solvent selected from
the group consisting of ethanol, acetone, acetonitrile, anisole, methyl ethyl ketone,
t-butyl methyl ether, dimethylacetamide, dimethylformamide, ethyl acetate, isopropyl
acetate, methanol, 2-methyltetrahydrofuran, methyl isobutyl ketone, toluene, tetrahydrofuran,
2-propanol / water mixtures, acetone / water mixtures and acetonitrile / water mixtures,
and isolating crystalline form A. Preferably the solvent is selected from the group
consisting of acetone and acetone / water mixtures. The Entinostat starting material
may also contain crystalline form C, wherein form C is characterized by a x-ray powder
diffraction pattern (XRPD) comprising peaks at 2θ values of 17.7°, 18.4°, 18.8°, 19.2°,
20.0°, 22.0°, 22.3°, 23.2° and 23.4°, measured at a temperature of about 20°C and
using Cu-Kα radiation (wavelength λ= 1.5418 Å), and still lead to the desired crystalline
form A.
[0032] Seed crystals may be added to any crystallization mixture to promote crystallization.
Seeding may be employed to control growth of a particular polymorph or to control
the particle size distribution of the crystalline product.
[0033] The crystalline Entinostat obtainable by the above mentioned processes is also an
embodiment of the present invention.
Advantages
[0034] Compression studies of crystal forms A, B and D showed all forms to maintain the
same polymorphic form with a slight crystallinity decrease. However crystal form D
produced an off-white disc, Form A a pale yellow disc and Form B a darker, beige coloured
disc with an uneven colour distribution across the disc surface. Therefore crystal
form D of the invention, unlike form A and B, allows an efficient removal of coloured
impurities.
[0035] The present invention provides a way to access highly pure crystal form A of Entinostat
starting from commercially available lower purity Entinostat by using crystalline
form D and E as an intermediate. The procedure is carried out under near ambient temperature
and does not require the use of strong acids, thereby avoiding degradation products
resulting from thermal or acid mediated decomposition.
[0036] In addition crystalline form D of Entinostat provides several benefits over the known
crystalline forms, since it exhibits substantially enhanced water solubility, which
in turn allows the preparation of a pharmaceutical composition of Entinostat exhibiting
improved dissolution in water. The water solubilities at 25°C of different crystal
forms of Entinostat have been measured by HPLC and are set out in the following table:
|
Form A |
Form B |
Form D |
Water solubility |
0.048 mg/mL |
0.028 mg/mL |
0.13 mg/mL |
Medical use and formulations
[0037] The crystalline forms of the invention may be used in the treatment of solid tumors,
including breast cancer, and hematologic cancers. They may be formulated with one
or more excipients or other active pharmaceutical ingredients to provide formulations
suitable for the treatment of the indications identified above. Such formulations
may optionally include one or more other components selected, for example, from the
group consisting of excipients, such as diluents, binders, disintegrants, lubricants,
preservatives and coating materials, and other active pharmaceutical ingredients of
different molecular structure. Alternatively crystalline form D may be converted to
crystalline form A as described above, which can be then used for the preparation
of suitable finished dosage forms.
X-ray Powder Diffraction (XRPD)
[0038] XRPD analysis was carried out on a PANalytical X'Pert Pro X-ray Diffractometer, scanning
the samples between 3 and 35 °2-theta. Material was loaded into a 96-well plate with
mylar film as the base. The samples were then loaded into the plate holder of a PANalytical
X'Pert Pro X-ray Diffractometer running in transmission mode and analyzed, using the
following experimental conditions:
Raw Data Origin: |
XRD measurement (*.XRDML) |
Scan Axis: |
Gonio |
Start Position [°2θ]: |
3.0066 |
End Position [°2θ]: |
34.9866 |
Step Size [°2θ]: |
0.0130 |
Scan Step Time [s]: |
18.8700 |
Scan Type: |
Continuous |
PSD Mode: |
Scanning |
PSD Length [°2θ]: |
3.35 |
Offset [°2θ]: |
0.0000 |
Divergence Slit Type: |
Fixed |
Divergence Slit Size [°]: |
1.0000 |
Specimen Length [mm]: |
10.00 |
Measurement Temperature [°C]: |
25.00 |
Anode Material: |
Cu |
K-Alpha [Å]: |
1.54060 |
K-Alpha2 [Å]: |
1.54443 |
K-Beta [Å]: |
1.39225 |
K-A2/K-A1 Ratio: |
0.50000 |
Generator Settings: |
40 mA, 40 kV |
Diffractometer Type: |
0000000011154173 |
Diffractometer Number: |
0 |
Goniometer Radius [mm]: |
240.00 |
Dist. Focus-Diverg. Slit [mm]: |
91.00 |
Incident Beam Monochromator: |
No |
Spinning: |
No |
Thermogravimetric/Differential Thermal Analysis (TG/DTA)
[0039] Approximately 5 mg of material was weighed into an open aluminium pan and loaded
into a Seiko TGA6200 (simultaneous thermogravimetric/differential thermal analyser
(TG/DTA)) and held at room temperature. The sample was then heated at a rate of 10°C/min
from 20°C to 300°C during which time the change in sample weight was recorded along
with any differential thermal events (DTA). Nitrogen was used as the purge gas, at
a flow rate of 300 cm
3/min.
Compression study
[0040] The compression study was performed using a Specac hydraulic press. A sample powder
(approx. 100mg) is loaded into a metal die (ring shaped metal holder). A snugly fitted
billet (a cylinder-shaped metal rod) is then placed into the die, on top of the powder
sample. The die and billet assembly is then placed into the hydraulic press and compressed
to a pressure of 5 tonnes/cm
2 and held under that pressure for 1h. The billet is then removed and the disc extracted
from the die.
[0041] The following non-limiting examples are illustrative of the disclosure.
EXAMPLES
Reference example 1
Step 1
[0043] To suspension of 4-(aminomethyl)benzoic acid and triethylamine in dichloromethane
(750 mL) precooled to 5°C was added trifluoroacetic anhydride within 1 hour. The mixture
was stirred at a temperature < 10°C for 3 hours and then acidified with concentrated
HCl (pH = 1). The resulting precipitate was filtered, washed with water and diethyl
ether and dried to give the desired product as a white solid.
Step 2
[0044] The product of Step 1 was suspended in dichloromethane (300 mL). DMF was added followed
by dropwise addition of oxalyl chloride within 30 min.. Then the mixture was stirred
at RT for 1 hour until completion on TLC and concentrated under reduced pressure.
The above-prepared acid chloride was re-dissolved in dichloromethane (50 mL) and was
added to a solution of Boc-o-phenyldiamine in pyridine (150 mL) and dichloromethane
(100 mL) precooled to 5°C within 30 minutes. Then the mixture was stirred for 2 hours
at RT, diluted with dichloromethane (300 mL) and a saturated solution of NaHCO
3 was added (300 mL). The layers were separated and the organic layer was washed with
a saturated solution of NaHCO
3 (300 mL) and brine (300 mL). The organic layer was dried and concentrated to give
a brown solid, which was suspended in diisopropyl ether (600 mL), stirred at RT for
30 minutes and filtered to give desired the product as an orange solid.
Step 3
[0045] The product from Step 2 was suspended in methanol / water and potassium carbonate
was added. The mixture was heated to 70°C and stirred overnight. Methanol was evaporated
and the product was extracted with dichloromethane (2 x 500 mL). The combined organic
layers were washed with saturated brine (300 mL), dried and concentrated to give the
desired product as red foam.
Step 4
[0046] To 3-pyridinemethanol dissolved in THF (467 mL) was added carbonyl diimidazole in
portions within 30 minutes. The mixture was then stirred at room temperature for 3
hours until no starting material was observed on TLC. The product from Step 3, dissolved
in THF (200 mL), was then added dropwise to the reaction mixture and stirring was
continued overnight. The mixture was diluted with ethyl acetate (500 mL) and washed
with brine (3 x 300 mL). The organic layer was dried and concentrated to give dark
brown foam. The crude reaction mixture was then purified via column chromatography
on SiO
2.
Step 5
[0047] The product from Step 4 was dissolved in methanol and 4 M HCl was added dropwise
within 1 hour. The mixture was stirred for 2 hours until completion on TLC and then
slowly poured into beaker containing a stirred solution of 1 M NaOH (800 mL). This
mixture was then diluted with dichloromethane (500 mL) and the layers were separated.
The aqueous layer was then extracted with dichloromethane (2 x 250mL). The combined
organic layers were washed with brine (2 x 250 mL), dried and concentrated to give
desired product as light brown solid. The crude solid was recrystallized from EtOH
(380 mL), cooled to 0°C and filtered, washed with cold EtOH (100 mL), dried to give
Entinostat as a beige solid.
[0048] The diffractogram of the product is shown in Figure 6 and shows the presence of another
crystalline phase in addition to crystal form A.
Reference example 2
Step 1
[0050] To suspension of carbonyl diimidazole in THF (214 mL) cooled to 10°C was added 3-pyridinemetanol
in THF (90 mL) and the mixture was stirred at RT for 1 hour. The mixture prepared
above was added dropwise to mixture of 4-(aminomethyl)benzoic acid, DBU, triethylamine
in THF (415 mL) and was stirred at RT for 14 hours. TLC analysis showed no starting
material. The THF was evaporated, and the mixture was diluted with water (600 mL)
and was acidified while stirring to pH = 5. The resulting white precipitate was filtered,
washed with water (600 ml) and methanol (150 mL) and dried to give 65.0 g of product.
Step 2
[0051] The product from Step 1 was suspended in THF. Carbonyl diimidazole was added in portions
within 30 minutes and the mixture heated to 60°C for 1.5 hours. According to TLC no
starting material was detected. The mixture was cooled to room temperature and treated
with o-phenyldiamine and TFA (added in one portion). The dark solution was stirred
at RT for 14 hours. THF was evaporated and the residue portioned between ethyl acetate
(1500 mL) and water (500 mL). The layers were separated and the water layer was extracted
twice with 250 mL of ethyl acetate. The combined organics were dried and concentrated.
The residue was suspended in dichloromethane (10 mL/g), stirred for 30 minutes, filtered
and dried (this procedure was applied twice) resulting in77 g of Entinostat as a beige
solid. The compound was analyzed by XRPD and resulted to be a mixture of form A and
form B.
Example 1
[0052] Entinostat (3 g) was dissolved in 1,4-dioxane (400 mL) and the solution volume was
reduced to ca. 10 mL by evaporation to produce a slurry, which was then stirred at
22°C. The solid was then filtered and analyzed and found to be Entinostat crystalline
form E. The XRPD and the DSC trace of the material are shown respectively in Figures
2 and 4.
[0053] Form E was slowly dried at 35°C for 4 weeks
in vacuo. The resulting solid was analyzed and found to be Form D. The XRPD and the DTA/TGA
trace of the material are shown respectively in Figures 1 and 3.
Example 2
[0054] Entinostat (3 g) was dissolved in 1,4-dioxane (400 mL) and the solution filtered
through a Whatman GF/F filter and evaporated to dryness. After analysis by XRPD, the
solid material was found to consist of poorly crystalline Form E. 1,4-Dioxane (6 mL)
was then added and the material was slurried at 22°C. The solid was then filtered
and slowly dried
in vacuo over 4 weeks at 35°C. The solid was then analyzed and found to be Entinostat crystalline
form D.
Example 3
[0055] Entinostat form D (400 mg) was suspended in acetone : water (9:1). The resulting
slurry was heated to 40°C and held at that temperature for ca. 2 hours and then filtered
through a 0.45 µm frit and the solution cooled to 5°C overnight. The collected solid
was then dried
in vacuo for 16 h, analyzed and found to be Entinostat crystalline form A.
Example 4
[0056] The experiment of example 3 is repeated using a mixture of crystalline forms C and
D. Crystalline form A is obtained.
1. Crystalline form D of Entinostat having a x-ray powder diffraction pattern comprising
peaks at 2θ values of 4.8°, 9.8°, 17.2°, 19.7° and 22.9°, measured at a temperature
of about 20°C and using Cu-Kα radiation (wavelength λ= 1.5418 Å).
2. The crystalline form according to claim 1 further characterized by a x-ray powder diffraction pattern comprising 2θ values of 4.8°, 9.8°, 12.8°, 14.7°,
17.2°, 18.4°, 19.7°, 21.8° and 22.9°, measured at a temperature of about 20°C and
using Cu-Kα radiation (wavelength λ= 1.5418 Å).
3. The crystalline form according to claims 1 to 2 characterized by a DTA/TGA trace showing an exotherm at 115°C and a melting endotherm at 151°C.
4. Crystalline form E of Entinostat having a x-ray powder diffraction pattern comprising
peaks at 2θ values of 3.8°, 15.3° and 21.6°, measured at a temperature of about 20°C
and using Cu-Kα radiation (wavelength λ= 1.5418 Å).
5. The crystalline form according to claim 4 further characterized by a x-ray powder diffraction pattern comprising 2θ values of 3.8°, 15.3°, 18.2°, 21.6°,
23.9° and 24.5°, measured at a temperature of about 20°C and using Cu-Kα radiation
(wavelength λ= 1.5418 Å).
6. The crystalline form according to claims 4 to 5 characterized by a DTA/TGA trace showing an endotherm at 80°C and a melting endotherm at 155°C.
7. The crystalline forms according to claims 1 to 6 in substantially pure form.
8. Crystalline form A of Entinostat having a x-ray powder diffraction pattern (XRPD)
comprising peaks at 2θ values of 18.4°, 18.8°, 19.1°, 20.9°, 22.6°, 26.4°, 26.7° and
27.2°, measured at a temperature of about 20°C and using Cu-Kα radiation (wavelength
λ= 1.5418 Å), in substantially pure form.
9. The crystalline forms according to claims 1 to 8 including less than 10%, preferably
less than 5%, more preferably less than 3%, most preferably less than 1% by weight
of other crystalline forms.
10. A pharmaceutical composition comprising the crystalline form D or the crystalline
form A of claims 1 to 3 or of claims 7 to 9 and a pharmaceutically acceptable carrier
or diluent.
11. The crystalline form D or the crystalline form A of claims 1 to 3 or of claims 7 to
9, or the composition of claim 10 for use as a medicament, preferably for use in the
treatment of breast cancer.
12. A process for the preparation of the crystalline form D of Entinostat of claims 1
to 3 comprising the step of drying crystalline form E of Entinostat.
13. A process for the preparation of the crystalline form E of Entinostat of claims 4
to 6 comprising the steps of suspending and/or dissolving Entinostat in a solvent
comprising dioxane, preferably in pure dioxane, and then isolating crystalline form
E.
14. A process for the preparation of crystalline form A of Entinostat, wherein form A
is characterized by a x-ray powder diffraction pattern (XRPD) comprising peaks at 2θ values of 18.4°,
18.8°, 19.1°, 20.9°, 22.6°, 26.4°, 26.7° and 27.2°, measured at a temperature of about
20°C and using Cu-Kα radiation (wavelength λ= 1.5418 Å), comprising the steps of contacting
the crystalline form D of Entinostat of claims 1 to 3 with a solvent selected from
the group consisting of ethanol, acetone, acetonitrile, anisole, methyl ethyl ketone,
t-butyl methyl ether, dimethylacetamide, dimethylformamide, ethyl acetate, isopropyl
acetate, methanol, 2-methyltetrahydrofuran, methyl isobutyl ketone, toluene, tetrahydrofuran,
2-propanol / water mixtures, acetone / water mixtures and acetonitrile / water mixtures,
and isolating crystalline form A.
15. Crystalline Entinostat obtainable by the process of claims 12 to 14.